Medical procedures and apparatus using intrabody probes

ABSTRACT

A medical probe such as a catheter ( 20 ) is guided within the body of a patient by determining the relative positions of the probe relative to another probe, as by transmitting non-ionizing radiation to or from field transducers ( 30, 230 ) mounted on both probes. In one embodiment, a site probe ( 28 ) is secured to a lesion within the body, and an instrument probe ( 200 ) for treating the lesion may be guided to the lesion by monitoring relative positions of the probes. Two or more probes may be coordinated with one another to perform a medical procedure.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims benefit and priority of the followingfive applications, and the disclosures of all of such applications areincorporated by reference herein:

U.S. application Ser. No. 60/012,275, filed Feb. 26, 1996

U.S. application Ser. No. 60/011,721, filed Feb. 15, 1996

U.S. application Ser. No. 60/031,824, filed Nov. 26, 1996,

Israel 119,262, filed Sep. 17, 1996

Israel 119,137, filed Aug. 26, 1996

The following PCT applications, each of which names Biosense, Inc as anapplicant are also incorporated by reference herein: Catheter BasedSurgery filed on or about Feb. 14, 1997 in the Israeli Receiving Office;Intrabody Energy Focusing filed on or about Feb. 14, 1997 in the IsraeliReceiving Office; Locatable Biopsy Needle, filed on or about Feb. 14,1997 in the Israeli Receiving Office; Catheter Calibration and UsageMonitoring filed on or about Feb. 14, 1997 in the Israeli ReceivingOffice; Precise Position Determination of Endoscopes filed on or aboutFeb. 14, 1997 in the Israeli Receiving Office; Medical Probes with FieldTransducers filed Feb. 14, 1997 in the United States Receiving Office;Catheter with Lumen filed Feb. 14, 1997 in the United States ReceivingOffice; Movable Transmit or Receive Coils for Location System filed Feb.14, 1997 in the United States Receiving Office; and IndependentlyPositionable Transducers for Location System filed Feb. 14, 1997 in theUnited States Receiving Office. The PCT application entitled,Multi-Element Energy Focusing, filed Feb 14, 1996 in the IsraeliReceiving Office and naming Victor Spivak as applicant is alsoincorporated by reference herein.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to medical probes having sensors fordetecting the disposition of the probe, and to the medical proceduresutilizing such probes.

BACKGROUND ART

Conventional surgical procedures involve cutting through bodilystructures to expose a lesion or organ within the body for treatment.Because these procedures create considerable trauma to the patient,physicians have developed minimally invasive procedures using probesinserted into the body through body orifices or through small holes totreat or measure structures within the body. For example, the devicescommonly referred to as endoscopes include an elongated body having adistal end and a proximal end. The distal end of the probe body can beinserted into the gastrointestinal tract through a body orifice. Theendoscope may be equipped with optical devices such as cameras or fiberoptics to permit observation of the tissues surrounding the distal end,and surgery may be performed by inserting and maneuvering surgicalinstruments through a channel in the endoscope body. Other probescommonly referred to as laparoscopes and orthoscopes are inserted intothe body through small holes formed in surrounding tissues to reach thebodily structures to be treated or measured. Still other probes,commonly referred to as catheters, can be advanced through the vascularsystem, as through a vein or artery, or through other bodily passagessuch as the urinary tract.

The physician can guide the probe to the desired location within thebody by feel or by continuously imaging the probe and the body, as byfluoroscopy, during the procedure. Where the probe includes opticalelements, the physician can guide the probe based on visual observationof the tissues surrounding the distal tip of the probe. However, thisoption is available only for probes such as conventional endoscopeswhich are large enough to accommodate the optical elements. Moreover,optical guidance normally is useful only where the distal tip of theprobe is disposed within a cavernous organ; it is not normally useful inguiding the probe within solid or semisolid tissues.

As described, for example, in U.S. Pat. Nos. 5,558,091, 5,391,199;5,443,489; and in PCT International Publication WO 96/05768, thedisclosures of which are hereby incorporated by reference herein, theposition, orientation or both of the distal end of a probe can bedetermined by using one or more field transducers such as a Hall effector magnetoresistive device, coil or other antenna carried on the probe,typically at or adjacent the distal end of the probe. One or moreadditional field transducers are disposed outside the body in anexternal frame of reference. The field transducers preferably arearranged to detect or transmit non-ionizing fields or field componentssuch as a magnetic field, electromagnetic radiation or acoustical energysuch as ultrasonic vibration. By transmitting the field between theexternal field transducers and the field transducers on the probe,characteristics of field transmission between these devices can bedetermined. The position and/or orientation of the sensor in theexternal frame of reference can then be deduced from these transmissioncharacteristics. Because the field transducer of the probe allowsdetermination of the position of the probe, such transducer is alsoreferred to as a “position sensor”.

As described, for example, in the aforementioned U.S. Pat. No.5,558,091, the frame of reference of the external field transducers canbe registered with the frame of reference of imaging data such asmagnetic resonance imaging data, computerized axial tomographic data, orconventional x-ray image data and hence the position and orientationdata derived from the system can be displayed as a representation of theprobe superimposed on an image of the patient's body. The physician canuse this information to guide the probe to the desired location withinthe patient's body, and to monitor its orientation during treatment ormeasurement of the body structure. This arrangement greatly enhances theability of the physician to navigate the distal end of the probe throughbodily structures. It offers significant advantages over conventionalmethods of navigating probes by feel alone. For instance, because itdoes not require acquisition of an optical image of the surroundingtissues for navigation purposes, it can be used with probes which aretoo small to accommodate optical elements, and can be used fornavigation of the probe within solid or semisolid tissues. Thetransducer-based system also avoids the difficulties associated withnavigation of a probe by continuous imaging of the probe and patientduring the procedure. For example, it avoids exposure to ionizingradiation inherent in fluoroscopic systems.

As described in certain embodiments taught in U.S. Pat. No. 5,391,199,the system can include one or more reference catheters and amapping/ablation catheter. Each of these catheters has a fieldtransducer as discussed above disposed adjacent the distal end of thecatheter. The mapping/ablation catheter is provided with electrodes fordetecting local electrical activity at the distal end of such catheter,and for applying radio frequency energy to ablate surrounding tissue.The reference catheters may be positioned with their distal tips atfixed locations within the heart, whereas the mapping/ablation cathetercan be moved within the heart while measuring electrical activity. Thetip positions of the reference catheter and of the mapping/ablationcatheter are monitored in the frame of reference of external antennas.Electrical activity data and positional data provided by themapping/ablation catheter provides a map of the electrical activity ofthe heart. The reference catheter position information can be used tocompensate for movement of the heart, and to register themapping/ablation catheter position data with images such as fluoroscopicor MRI images. In certain procedures taught in the '199 patent, the mapcan be used to locate a site within the heart for treatment, and theposition information provided by the position sensors can be used tomaneuver the mapping/ablation catheter to the treatment site.

However, still further improvements in transducer-based probe navigationand treatment systems would be desirable. In particular, it would bedesirable to provide accurate guidance of a probe without reliance onregistration between the sensor-based positional data andpreviously-acquired image data. This would be particularly desirable forplacement and treatment of a probe in relatively soft, mobile tissuessuch as the breasts, lungs, liver, gastrointestinal tract and otherinternal organs. Moreover, it would be desirable to provide a systemwhich provides probe guidance information to the physician in a formwhich can be readily assimilated and used by the physician. It wouldalso be desirable to provide a system which facilitates the use ofmultiple probes in combination to treat, observe or measure a bodystructure.

DISCLOSURE OF THE INVENTION

The present invention addresses these needs.

One aspect of the present invention provides methods of guiding medicalinstruments. A method according to this aspect of the inventiondesirably includes the steps of providing a site probe at a site withinthe body of a patient and providing an instrument probe to be guidedwithin the body of the patient. The method further desirably includesthe step of transmitting one or more fields to or from each of theprobes and detecting each such transmitted field. The relativedisposition of the site probe and the instrument probe is determinedfrom the properties of the detected fields and the instrument probe isdirected toward the site probe on the basis of the so determinedrelative disposition. As used in this disclosure with reference to asingle probe, the term “disposition” refers to the position of theprobe, the orientation of the probe, or both. As used in this disclosurewith reference to any two probes, the term “relative disposition” refersto the direction from one probe to the other, the distance from oneprobe to the other, or both. Thus, in determining relative disposition,the direction from one probe to the other, or the distance from oneprobe to the other can be determined. Preferably, however, bothdirection and distance are determined so as to completely determine therelative positions of the two probes. The orientations of one or bothprobes may also be determined.

For example, magnetic, electromagnetic or acoustic fields may betransmitted between external field transducers and field transducers onthe site and instrument probes, so that the position of each such probeis determined in a common frame of reference provided by the externaltransducers. The position of the instrument probe relative to the siteprobe can be determined by subtracting the position vectors of the twoprobes in the external antenna frame of reference. The step of directingthe instrument probe relative to the site probe may include the step ofpointing the instrument probe in a particular direction relative to thesite probe, such as pointing the instrument probe in a direction towardthe site probe. Preferably, the step of directing the instrument probetoward the site probe in response to the determined relative dispositionincludes the step of moving the instrument probe in a particulardirection relative to the site probe, most preferably moving theinstrument probe toward the site probe. In preferred methods accordingto this aspect of the invention, the site probe acts as a marker and theinstrument probe is guided toward the marker.

The step of determining the relative dispositions of the probes mayinclude the step of transmitting a field from the position sensor on oneprobe to the position sensor on another probe and determining therelative dispositions based upon the characteristics of suchtransmission. For example, the position sensor on the site probe may bearranged to emit electromagnetic or ultrasonic radiation, whereas theposition sensor on the instrument probe may be arranged to monitor theamplitude of radiation received at the tip of the instrument probe. Theamplitude of the received radiation constitutes a measure of thedistance between the probes.

Alternatively, the relative dispositions of the probes can be determinedby monitoring fields transmitted between the probes. For example, thesite probe field transducer may include or consist of a permanent magnetarranged to provide a magnetic field. The instrument probe fieldtransducer may be adapted to determine the direction of the magneticfields prevailing at the distal end of the instrument probe, therebyproviding an indication of the direction from the instrument probe tothe site probe. The intensity of the magnetic field can be used anindication of distance from the site probe in such an arrangement. Inyet another arrangement, the site probe may be arranged to emitultrasonic or electromagnetic radiation. The instrument probe may beguided to the site probe by moving it in the direction of increasingfield amplitude. The instrument probe may be provided with a fieldtransducer capable of detecting the amplitude of such radiation. Thesite probe may include a guidewire or other elongated member and thesite probe may emit the field along the length of such elongated member.

In a particularly preferred arrangement, the site probe is placed at asite which requires treatment, testing or another medical procedure. Forexample, the site probe may be placed in or near a lesion during animaging procedure such as mammography or other x-ray procedures,magnetic resonance imaging or CAT scanning capable of imaging the lesionand the site probe. After the site probe is placed, a surgical procedureto remove or repair the lesion may be performed by moving the distal endof an instrument probe toward the site probe and performing the requiredtreatment using the instrument probe. As the site probe is anchored inthe patient's tissue in or adjacent the lesion, the instrument probe canbe guided accurately to the lesion even if the patient's tissues shiftor deform. It is not necessary to image the patient during the treatmentprocedure. Therefore, the treatment procedure can be conducted withoutthe physical encumbrance of the imaging apparatus and without exposingthe physician or patient to additional radiation from the imagingapparatus.

In another preferred embodiment, a device implanted within the patientfor long-term treatment purposes may be provided with a field transducerso that the device can be located and removed. For example, the heartpacemaker leads, which are implanted within a patient, sometimes break,leaving the distal portion of the lead implanted in the patient. Eachsuch lead may be provided with a field transducer before implantation,so that the detached lead portion can be located and removed in the samemanner as the lesions discussed above.

In a further preferred embodiment, a passageway such as a fistula orshunt can be formed within a bodily structure by placing the site probeat an ending location corresponding to one end of the desiredpassageway; placing the instrument probe at a starting locationcorresponding to the opposite end of the desired passageway and thenmoving the instrument probe through the tissues to be penetrated whileguiding the motion of the instrument probe toward the site probe usingthe detected relative positions of the two probes. In effect, the siteprobe serves as a target and the passageway is formed by moving theinstrument probe through the tissues toward the target. In a variant ofthis approach, the instrument probe is pointed toward the site probe anda substance or energy capable of destroying tissue is emitted from theinstrument probe toward the site probe, thereby boring the hole from thestarting location to the ending location.

Yet a further aspect of the present invention provides a method ofmaking a intrahepatic portal-systemic shunt, i.e., a shunt from thehepatic vein to the portal vein. Such shunts have been providedheretofore to relieve blockage of the portal vein arising from cirrhosisor other disease of the liver. Such a shunt serves to reduce theelevated venous pressure prevailing in this condition. According to thisaspect of the present invention, an instrument probe such as a needle isguided from a starting location in the hepatic vein or the portal veinto an ending location in the opposite one of these veins, i.e., from thehepatic vein to the portal vein or from the portal vein to the hepaticvein. The guidance is performed using a field transducer on theinstrument probe and using non-ionizing fields transmitted to or fromsuch field transducer. In one arrangement according to this aspect ofthe invention, a site probe as discussed above is positioned at theending location, i.e., in or near the portal vein or the hepatic veinand the needle or instrument probe is guided toward the ending locationon the basis of the relative positions of the site probe and instrumentprobe. In another arrangement, the instrument probe position can bedetermined in a frame of reference such as the frame of reference ofexternal field transducers and the positional information can beregistered with a previously acquired image of the liver, so that arepresentation of the needle can be superimposed on an image of theliver. Still further aspects of the present invention include methods oftreating tissues within the lungs by guiding an instrument probe such asa bronchoscope within the lung using non-ionizing fields transmitted toor from the instrument probe. Preferred methods according to this aspectof the present invention utilize a site probe disposed in the lungtissue at or near the location to be treated, and provide guidance bymonitoring the relative position of the instrument probe and site probe.

Yet another aspect of the present invention provide methods ofperforming medical procedures using two or more probes. Methodsaccording to this aspect of the present invention include the step ofproviding first and second probes, each probe having a field transducermounted thereon, and determining the relative dispositions of the twoprobes. Methods according to this aspect of the invention preferablyfurther include the steps of determining the relative dispositions ofthe two probes using non-ionizing fields transmitted to or from theposition sensors on the probes; performing a first medical procedurewith the first probe and a second medical procedure with the secondprobe and coordinating the two medical procedures using the determinedrelative dispositions. For example, where the medical procedureperformed by the first probe involves tunneling, cutting or excavatingtissues, the medical procedure performed by the second probe may includeimaging, of the region treated by the first probe; evacuation of debrisfrom the region treated by the first probe or any other procedure whichcan benefit by maintaining the two probes in defined spatialrelationship to one another.

Yet another aspect of the present invention provides methods ofperforming medical procedures which also use first and second probes.Procedures according to this aspect of the present invention include thesteps of providing first and second probes, each having a fieldtransducer thereon; performing a medical procedure at a location usingthe first probe; determining the relative positions of the probes andperforming a medical procedure at a second location having apredetermined spatial relationship to the first location using thesecond probe. In this procedure, localization of the medical procedureperformed by the second probe is based on the determined relativedispositions of the two probes. That is, the region of the patient'sbody treated, measured or imaged in the second medical procedure may beselected or controlled based upon the relative dispositions of the twoprobes. Provided that the first probe is located in the requireddisposition relative to the body of the patient, both probes will be inthe required disposition relative to a structure in the body of thepatient, and relative to one another. The first and second locations maybe identical to one another, so that both probes act at the same point.The first and second locations may be different from one another, inwhich case the first and second locations may be related to a commonbody structure. For example, where the first probe is positioned at apoint along an intrabody lumen such as an artery or vein, the relativedisposition of the first and second probe may be selected so that thesecond probe is disposed at another point in the same artery or vein. Ineach of the aforesaid methods, additional probes having fieldtransducers thereon may be employed as well.

Yet another aspect of the present invention provides a site probe formarking a site within the body of a medical patient. A site probeaccording to this aspect of the present invention preferably includes afield transducer in the form of a sensor adapted to detect anon-ionizing field such as a magnetic or electromagnetic field or anacoustic field and to provide one or more sensor signals representingone or more properties of the so detected fields. The site probeaccording to this aspect of the present invention may further include ananchor adapted to fasten the field transducer to tissue within the bodyof the living patient and signal transmission means for conveying thesensor signals from within the body of the patient to outside of thebody of the patient.

Alternatively, a site probe for marking a site within the body of apatient may include a field transducer which incorporates an antenna orother transducer adapted to transmit a non-ionizing field in response toone or more drive signals, a site probe body housing the device, and ananchor adapted to fasten the site probe body to tissue within the bodyof the patient. A site probe according to this aspect of the presentinvention preferably includes signal transmission means for transmittingthe drive signals from outside the body of the patient to the devicewhile the device is disposed within the body of the patient.

The anchor may include a mechanical device such as a screw havingthreads adapted to engage tissue or a pincer incorporating a pluralityof flexible or movable times adapted to engage tissue within thepatient's body. The site probe as described above may be provided in anassembly together with an elongated probe such as a catheter havingdistal and proximal ends. The site probe may be releasably mounted tothe elongated probe adjacent the distal end thereof so that the siteprobe can be advanced within the body of the patient while the proximalend of the elongated probe remains outside of the body, anchored to thepatient tissue at a desired location within the body and left within thepatient's body. The signal transmission means incorporated in the siteprobe may include one or more leads extending from the sensor towardsthe proximal end of the elongated probe, these leads being arranged sothat the elongated probe can be withdrawn leaving the leads in positionafter the site probe has been fastened to the tissue by the anchor.

Further aspects of the present invention provide apparatus for guidingan instrument to a site within a patient comprising a site probe asaforesaid and an instrument probe adapted for insertion within the body.The instrument probe has a field transducer mounted thereon adapted tosend or receive fields of the type sent or received by the site probe.The apparatus may further include one or more external field transducersadapted for disposition outside of the patient's body and drive meansfor actuating the field transducers of the site probe, the instrumentprobe and, where provided, the external field transducers to transmitone or more non-ionizing fields therebetween and detect eachso-transmitted field. As discussed above in connection with the method,the relative dispositions of the instrument probe and site probe may bedetermined from the detected fields.

These and other objects, features and advantages of the presentinvention will be more readily apparent from the detailed description ofthe preferred embodiments, taken in conjunction with the accompanyingclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic view depicting a probe in accordance with oneembodiment of the invention.

FIG. 2 is a view similar to FIG. 1 but depicting a probe in accordancewith a further embodiment of the invention.

FIG. 3 is a fragmentary view depicting a probe in accordance with yetanother embodiment of the invention.

FIG. 4 is a view similar to FIG. 1 but depicting a probe in accordancewith yet another embodiment of the invention.

FIG. 5 is a diagrammatic perspective view depicting a patient andapparatus during performance of a process in accordance with oneembodiment of the invention.

FIG. 6 is a diagrammatic elevational view taken on an axial planedepicting a patient and apparatus during a further process in accordancewith another embodiment of the invention.

FIG. 7 is an elevational view of the same patient and apparatus of FIG.6, but taken along a saggital plane.

FIG. 8 is a fragmentary diagrammatic view depicting elements ofapparatus in accordance with yet another embodiment of the invention.

FIG. 9 is a fragmentary diagrammatic view depicting elements ofapparatus in accordance with a further embodiment of the invention.

FIG. 9A is a fragmentary diagrammatic view depicting elements ofapparatus in accordance with a another embodiment of the invention.

Each one of FIGS. 10 through 17 is a fragmentary, diagrammatic viewdepicting apparatus and portions of a patient during procedures inaccordance with a further embodiment of the invention

FIG. 18 is a an elevational view depicting a computer screen displayutilized in certain embodiments of the invention.

MODES FOR CARRYING OUT THE INVENTION

A site marking probe assembly in accordance with one embodiment of theinvention includes an elongated probe in the form of a tube or catheter20 having a proximal end 22, a distal end 24 and an elongated bore 26extending between such ends. A site probe body 28 incorporating aposition sensor or field transducer 30 is physically connected to ananchor in the form of a set of hooks or grapples 32. Field transducer 30is provided in the form of a sensor arranged to detect magnetic orelectromagnetic fields. For example, the sensor 30 may be a multiaxis,solid-state position sensor of the type disclosed in the aforementionedU.S. Pat. No. 5,558,091. Such a sensor incorporates a plurality oftransducers sensitive to magnetic field components in mutuallyorthogonal directions. Other suitable position sensors include coils asdisclosed in the aforementioned U.S. Pat. No. 5,391,199 and in PCTApplication PCT/US95/01103, now published as PCT InternationalPublication WO 96/05768, the disclosure of which is hereby incorporatedherein by reference. Such coils may be provided as a single coil or as aplurality of orthogonal coils capable of detecting field components inorthogonal directions. Position sensor or field transducer 30 isconnected to leads 34 which extend through bore 26 to and beyond theproximal end 22 of tube 20. Connectors 35 are provided at the proximalends of leads 34. A control rod 36 in the form of a flexible shaftextends axially within bore 26 from outside the proximal end 22 of thetube to the site probe body 28. Control rod 36 may be a braided cable orother flexible element capable of bending and deforming along with tube20, but also capable of transmitting axial thrust. Elongated probe ortube 20 is constructed and arranged to reach within the body of thepatient to the desired location. For example, tube 20 may have thestructure of a conventional catheter, bronchoscope, endoscope,laparoscope or the like. The size and shape of tube 20 will depend uponthe region of the body to be treated. Tube 20 may be steerable orguidable, and may be provided with features as discussed below forselectively bending its distal end.

Site probe body 28 is releasably engaged within bore 26 adjacent distalend 24 so that the body 28 and hence grapples 32 can be displaced out ofthe distal end 24 of the tube. Grapples 32 are spring-loaded so thatthey tend to expand to the positions indicated in broken lines at 32′ inFIG. 1 when the device is displaced out of the distal end of the tube.The spring-loaded grapples 32 may provide frictional engagement with thewall of tube 20 while the device is disposed inside the tube and thusmay serve to releasably retain the device in the tube. As furtherdiscussed below, in use the assembly is advanced until distal end 24 isdisposed adjacent a lesion L or other tissue of interest within thepatient's body. At that point, body 28 and anchor or grapples 32 areadvanced forwardly by control rod 36, thereby dislodging the device fromwithin tube 20 and engaging grapples 32 with the tissue of lesion L atthe distal end of the assembly as indicated at 32′. In this condition,site probe body 28, and hence sensor or field transducer 30 are securedto the tissue of lesion L by the grapples.

Tube 20 may be removed, leaving control rod 36 and leads 34 in place.During the removal process, the tube 20 slides in a proximal directionover control rod 36, leads 34 and connectors 35, so that the control rodand leads pass out of the distal end 24 of bore 26. To facilitatemovement of the control rod and leads through the bore tube, the controlrod and the leads may be formed integrally with one another. Also,although only tube leads are depicted in FIG. 1, it should beappreciated that the number of leads will depend upon the configurationof position sensor 30.

An assembly according to a further embodiment of the invention (FIG. 2)incorporates a tube 120, site probe body 128; sensor or field transducer130; control rod 136 and leads 134 similar to the corresponding elementsof the assembly in FIG. 1. However, this assembly includes an anchor inthe form of a screw 132 in place of the grapples used in the embodimentof FIG. 1. In use, control rod 136 is used to turn active element 128and hence screw 132 while forcing active element out of the interior oftube 120, thereby leaving the active element anchored to the tissue bythe screw as indicated in broken lines at 132′.

As indicated in FIG. 3, the screw or grapples can be replaced by aneedle 140 affixed to the active element body. The needle is providedwith a barb 142. Here again, the active element body and the anchor areforced distally out of the distal end 124 of the tube so that the anchorengages the tissue. Barb 142 holds the active element body and sensor inplace. Assemblies according to this aspect of the invention may includemany different forms of anchors, in addition to the barbs, screws andgrapples discussed above. Various devices which can be implanted andmechanically engaged in the tissue of a patient are shown in U.S. Pat.Nos. 5,217,484; 5,195,540; 4,592,356; 4,931,059; 5,234,426; 5,267,960;5,409,004; 5,158,084; 5,059,197; 5,197,482; and 5,301,682. All of thesepatents teach mechanical devices for fastening a device to the tissue ofa patient, for marking a lesion or for other purposes. Essentially anymechanical device which can be actuated to anchor the active device bodyto the patient's tissue can be employed as the anchoring device instructures as depicted in FIGS. 1-3. Further, although it is preferredto insert the active device body through a tubular element as shown, thesame is not essential. For example, the site probe may incorporate asite probe body in the form of a rigid needle housing the fieldtransducer so that the needle, with the position sensor disposedadjacent the distal end of the needle, can be advanced into the body.Such a needle can be placed by itself, without any external covering, byadvancing the needle into the patient's tissues. Such a rigid needle canbe provided with anchors as discussed above to hold the needle in placeafter insertion in a method according to one embodiment of theinvention. Similarly, the site probe body can be integrated with theelongated flexible bodies discussed above. For example, transducer 30and grapples 32 (FIG. 1) could be mounted to elongated probe body 20, inwhich case the elongated probe body would be left in place.

Apparatus according to the present invention preferably also includes aninstrument probe 200 (FIG. 4). The instrument probe may incorporateessentially any device which can be inserted or advanced into the bodyto perform a medical procedure, such as treatment, measurement orobservation. As used herein, the term “treatment” includes capturingsamples of tissues or materials present within the body, and thusincludes biopsies. As illustrated, instrument probe 200 includes atubular body 202 having a handle portion 204 affixed to a proximal endof the body and having a distal portion 206 remote from handle 204. Body202 has a bore 208 extending longitudinally from its proximal end to itsdistal end and open to the outside through handle 204. Body 202 mayincorporate a flexible section adjacent the distal end, so that thedistal end 206 can be bent or pivoted relative to the remainder of thebody. The body of the instrument probe defines a long axis 237 at end206, and axes 239 and 241 orthogonal to axis 241. Probe 200 mayincorporate devices (not shown) for bending the distal end of body 202relative to the remainder of the body and thereby steer the device as itis advanced into the patient's anatomy. Movement of end 206 around axis237 is commonly referred to as “roll”, whereas movements of the endaround axes 239 and 241, such as encountered during bending of the bodyor during tilting of the entire device, are referred to as “pitch” and“yaw” respectively. These elements of the instrument probe may besubstantially conventional, and may be of the types commonly utilized insteerable catheters, needles, endoscopes and other probes. Bore 208 isarranged to accommodate a conventional intrabody medical instrument suchas scissors or forceps, or other surgical tool 210 operable from theproximal end or handle of the device. Surgical tool 210 may be anyconventional surgical tool of the type commonly used in endoscopic,arthroscopic, laparoscopic surgical procedures, or a conventional biopsysampling device. The tool is arranged so that it can be advanced to anoperative position 210′ outside of the distal end of body 202. Tool 210is arranged so that it can be manipulated and controlled from theproximal end or handle 204 of the body. Thus, the tool is connected to amanipulating handle 212 by conventional control elements or linkages.Other expedients for manipulating and controlling a tool at the distalend of body 202 can be employed as, for example, electrical, electronicor optical control linkages. Alternatively, tool 210 can be mounted infixed position on body 202 or formed integrally therewith as, forexample, where body 202 is equipped with a cutting blade. For example,body 202 may be a biopsy needle of generally conventional construction,or else may be a biopsy needle of the type described in the copending,International Application, entitled “Locatable Biopsy Needle”, namingBiosense, Inc. as an applicant and filed in the Israeli Receiving Officeon even date herewith, the disclosure of which is hereby incorporated byreference herein. The instrument probe may incorporate a conventionalsurgical instrument such as a scalpel, forceps, or other instrumenthaving parts which can be advanced into the patient's body to perform asurgical or medical procedure at a place within the patient's body. Tool210 may be a device for measuring or sensing phenomena within the body,such as a thermometer or electrode for measuring intrabody potentials; adevice for imaging structures within the body, such as an optical orultrasonic camera or other imaging device; a device for dispensingmedications; a device for applying therapeutic radiation; or any otherdevice which can be used to treat, measure or observe structures withinthe body of a living subject.

A field transducer or position sensor 230 is mounted in instrument probebody 202 adjacent the distal end 206 thereof. Transducer 230 may be ofthe same types as discussed above with reference to the position sensorsof the site probes. Transducer 230 is connected via leads 234 to theproximal end or handle 204 of the body. Leads 234 are provided withexposed terminals or connections 235 at the proximal end of the body. Ifthe instrument probe incorporates a rigid or substantially rigid body,the field transducer 230 can be mounted at essentially any location onthe body having a defined spatial relationship to the operative portionsof the instrument, such that the disposition of the operative portionscan be deduced from the disposition of the field transducer. However,where the instrument probe is flexible, the field transducer preferablyis mounted adjacent any operative portions of the tool incorporated inthe instrument probe, so that the disposition of the operative portionsof the tool included in the instrument probe can be deduced from thedisposition of the field transducer.

The apparatus further includes a set of field transducers or antennas300 mounted in a frame of reference external to the patient. Forexample, field transducers 300 may be mounted to a patient-supportingbed. Antennas 300 are linked to a field transmitting and receivingdevice 302 and a computer 304, which in turn is linked to a displayeddevice such as a cathode ray tube 306. These elements are arranged tocooperate with the field transducers or position sensors on the siteprobe and on the instrument probe to determine the dispositions of thefield transducers on the probes, and hence determine the dispositions ofthe site probe and the instrument probe in the frame of reference of theexternal field transducers or antennas. These elements of the apparatuscan be as described in the aforementioned '091 or '199 patents. Otherdevices for detecting disposition of probes equipped with positionsensors by transmission of non-ionizing fields are known in the art. Asis known in the art, electromagnetic or magnetic fields can betransmitted between an antenna or field transducer mounted in anexternal frame of reference and a position sensor or field transducer ona probe, and the disposition of the probe can be calculated from thecharacteristics of the fields detected by the transducer on the probe.Thus, the external field transducers or antennas and the position sensoror field transducer on the probe cooperatively define a plurality oftransmitter-receiver pairs. Each such pair includes one transmitter andone receiver as elements of the pair. One element of each such pair isdisposed on the probe and the other element of each such pair isdisposed at a known disposition in the external frame of reference.Typically, at least one element of each transmitter-receiver pair isdisposed at a different position or orientation than the correspondingelement of the other pairs. By detecting the characteristics of fieldtransmission between elements of the various pairs, the system candeduce information concerning the disposition of the probe in theexternal frame of reference. The disposition information can include theposition of the probe, the orientation of the probe or both.

In a method according to one embodiment of the invention, site probebody 28 is positioned and anchored on a lesion L within the patient'sbody during a conventional radiologic procedure. For example, while thepatient is undergoing fluoroscopic, X-ray or other imaging examinationof the lungs, the site probe assembly is advanced to a lesion observedin such examination, and the site probe body 28 is anchored on thelesion using guidance provided by the imaging procedure. The anchoringelement such as grapples 32 is actuated to anchor the site probe body inplace on the lesion, and the tubular body 20 is withdrawn, leaving leads34 protruding from the patient's body.

After the site probe has been placed, the patient is positioned in theframe of reference of the external field transducers or antennas 300.Leads 34 are connected to the field transmitting and receiving unit 302,thereby connecting the field transducer or position sensor 30 on thesite probe to the transmitting and receiving unit. Similarly, the fieldtransducer or position sensor 230 of the instrument probe (FIG. 4) isconnected to the transmit/receive unit 302 through leads 234. The distalend 206 of the instrument probe is advanced into the patient towards thelesion, carrying the position sensor or field transducer 230 with it.The field transmitting and receiving unit 302 and computer 304 actuatesexternal field transducers or antennas 300 and the field transducers orposition sensors 30 and 230 of the probes to transmit and receivefields. Where the external devices or antennas 300 are used as fieldtransmitters, the leads 34 and 234 from the probes will provide sensorsignals representing the fields detected at the probes to the fieldtransmit and receive unit. Conversely, where the field transducers orposition sensors on the probes are used as transmitters, leads 34 and234 can be used to send drive signals to field transducers or positionsensors 30, 230 on the probes. In the conventional manner, the computer304 deduces the disposition of the field transducers on the probes andthus deduces the disposition of the probes themselves in the frame ofreference defined by the external field transducers. In the arrangementshown, the computer deduces the position of probe 28 and causes the sameto be displayed at a location 28′ on display unit 306 and likewisededuces the position of the distal end 206 of the instrument probe anddisplays the same at a location 206″ on display 306. Display of the twolocations provides a visual indication of the distance and directionfrom the distal end 206 of instrument probe 200 to the site probe body28. This guides the physician as he or she advances the instrument probetoward the site probe through the patient's tissues.

Because the site probe is mounted in the patient's body at or adjacentto the lesion or other tissue to be treated, the actual position of thelesion or tissue will not affect operation of the system. Thus, thepatient can move in the external frame of reference, and the lesion ortissue may move within the patient. For example, the lung being treatedmay be deflated after placement of the site probe but before the othersteps of the procedure. Nonetheless, the system will continue to displaythe correct position of the instrument probe distal end and the siteprobe, and will continue to provide proper guidance for navigating theinstrument probe towards the lesion or other tissue to be treated. Asused in this disclosure, the terms “navigation” and “navigating” referto the process of moving a probe within the body of a patient to adesired location. During the navigation procedure, the physician mayrely on additional information and cues such as his or her knowledge ofthe anatomy and feel of the instrument probe as the same is advancedthrough the patient's body. Where conventional visualization devicessuch as cameras or fiber optic devices are provided on the instrumentprobe, these may be used to provide additional guidance. Also, thesystem may augment the display 306 by providing a prominent indicationof the direction from the instrument probe distal end to the site probeas, for example, a bold arrow 308 extending in that direction. Theindicia representing the instrument probe and the site probe on thedisplay may have different characteristics, such as different colors orshapes, so that the physician can readily distinguish them from oneanother.

The display need not show any image of the patient's tissues. However,if previously acquired image data is readily available and can bereadily registered with the probe position data, the previously acquiredimage data can be displayed in registration with the indiciarepresenting the probes.

As shown in FIGS. 6 and 7, the display of positions can be provided inmultiple planes. Thus, display unit 306 may incorporate a pair ofdisplay screens 352 and 356 disposed in perpendicular planes. Each suchdisplay unit may display only components of position in directionsparallel to the plane of that screen. For example, screen 356 isdisposed in a plane perpendicular to the long axis of the patient's bodyand thus presents an axially directed view showing the representation206″ of the instrument probe tip and the representation 28″ of the siteprobe body in the correct relative positions. Screen 352 is disposed ina plane parallel to the longitudinal axis of the patient's body andpresents a saggital view of the relative positions. Other convenientforms of representing three dimensional information can also beemployed. For example, the relative positions can be displayed in astereoscopic imaging device such as a binocular imaging device of thetype currently used in “virtual reality” computer graphics applications,in a holographic image or in any other form of three dimensional imagingdevice. Once the physician has moved the distal tip of the instrumentprobe to the location of interest, the physician can perform a medicalprocedure as, for example, a procedure to remove the lesion in itsentirety or to perform a biopsy on the lesion. During or after theprocedure, site probe body 28 is removed. Where the tissue to which thesite probe is anchored is cut from the patient during the procedure, thesite probe can simply be pulled out of the patient by means of thecontrol rod 36 (FIG. 1). Alternatively, the anchoring device used in thesite probe may permit removal of the site probe from the tissue withoutremoving the tissue. For example, screw 132 (FIG. 2) can be releasedfrom the tissue by turning the associated control rod 136. A grapplearrangement may be provided with articulating elements which can becontrolled by operation through the control rod, so that the grappleacts as a controllable pincer. In this event, the site probe can bereleased from the tissue by actuating the grapple to release the tissue.

Computer 304 can calculate the relative positions of the instrumentprobe distal end 206 and site probe body 28 by subtracting the positionsof the two probes. That is, the system may substract the coordinates ofthe site probe distal end in the external frame of reference defined byexternal field transducers 300 from the coordinates of the site probebody 28 in the same frame of reference to arrive at the components ofthe relative position vector from the instrument probe distal end to thesite probe body. The relative positions can be provided as a humanperceptible indication other than a visual display as, for example, atactile display or one or more audible signals provided to the physicianduring navigation of the instrument probe. The calculated relativeposition can be displayed numerically as well as graphically as, forexample, by displaying the individual components of the relativeposition vector. Also, where the instrument probe is manipulated byautomated equipment, the relative position can be provided as vectorcoordinates or any other convenient form to the automated equipment soas to control the movement of the instrument probe toward the site probeautomatically.

As shown in FIG. 8, a reference probe 328 having a reference probe fieldtransducer or position sensor 330 thereon may be used in conjunctionwith site probe 28. Thus, the reference probe may be positioned in thepatient's body adjacent the site probe during the procedure used toplace the site probe. The position monitoring system detects theposition of the reference probe in the same manner as it detects thepositions of the site probe and instrument probe. Any substantial changein the relative positions of the site probe and reference probeindicates that one or the other of these probes has become dislodgedfrom the tissue to which it is anchored. The system may be arranged toissue an automatic warning to the physician, such as a warning tone orvisual indication upon occurrence of this condition. Also, the relativedisposition of the site probe and reference probe may be recorded duringthe placement step as, for example, from x-ray or other image dataacquired during the placement procedure. This prerecorded dispositiondata can be compared to the relative disposition of the site probe andthe reference probe acquired from the field transducers. Here again, anysubstantial change in the distance between the site probe and thereference probe indicates that one of the probes has become dislodged.

In the arrangements discussed above, the probes are connected byconductors to the external field transmitting or receiving device.However, such a hard-wired connection is not essential. For example, asshown in FIG. 9, a site probe 428 may include a field transducer in theform of an inductive antenna 430 linked to a capacitor 431 to form aresonant circuit. The external field transducers may apply drive signalsin the form of alternating electromagnetic fields to the site probe atthe resonant frequency of the circuit in the site probe. The site probewill then radiate electromagnetic fields at the same frequency. Such anarrangement can be used, for example, in a time-multiplex system. Duringsome intervals, the external field transducers are actuated to drive thesystem. During other intervals the external devices are used asreceiving antennas. Alternatively, the reradiating circuit in the siteprobe may be arranged to receive signals at one frequency and totransmit reradiated signals at a different frequency. As shown in FIG.9A, a site probe may incorporate a small biocompatable metal pellet 450with a field transducer in the form of a magnetic metallic element suchas 460 disposed therein. In the presence of an externally appliedalternating magnetic field, such a pellet will emit a field at the samefrequency but out of phase with the external field, thereby altering thephase of the field in the vicinity of the pellet. The degree of phasealteration varies with distance from the pellet over a small regionsurrounding the pellet. The field transducer of the instrument probe maydetect the alternating field, and the phase of the field may be used asan indication of distance from the site probe. Site probes of thisnature may be used to mark multiple locations within the body. Suchprobes can be applied by injection using a syringe and can be fixed inplace using a biocompatable adhesive. Site probes which are powered byradiated fields, such as those discussed above with reference to FIGS. 9and 9A, are particularly useful for long-term implantation. Providedthat the site probe remains in place, the instrument probe can benavigated back to the same site even after a long time has elapsed, andeven if the site has moved within the body due to growth, healing orother long-term processes. Still other arrangements can use aself-powered site probe, incorporating a storage battery or other sourceof energy and an internal field generating device such as an oscillatorlinked to an antenna. Battery-powered site field transducers areparticularly useful for applications where the field transducer must beactive only for a short time as, for example, where a site probe is usedto mark a lesion which will be removed promptly after the fieldtransducer is activated. Alternatively, a battery-powered fieldtransducer may be installed in a long-term application and activated byan externally-applied signal or internal occurrence. More complex formsof such radiating devices can incorporate multiple field transducers orantennas in orthogonal directions for radiating multiple fields. Thesemay be operated at different frequencies or according to a time divisionmultiplexing scheme. Similar arrangements can be used for the instrumentprobe.

Still other forms of field transducers may be arranged to radiateacoustic fields. Optical radiation, such as visible or infrared light,may also be employed. Many tissues within the body are translucent atred and infrared wavelengths, so that the intensity of optical radiationemitted from a field transducer such as a light emitting diode can beused as an indication of distance from that transducer.

In a system according to yet another embodiment of the invention, thesite probe body has a field transducer in the form of a permanent magnet530 mounted therein. The instrument probe has a field transducer 531which is adapted to measure constant magnetic field components in aplurality of orthogonal directions in a frame of reference fixed to thedistal end 506 of the site probe body. For example, field transducer orposition sensor 531 may include a plurality of magnetoresistive, Halleffect or other similar solid state magnetic field transducers, eachsuch transducer being sensitive to a field component in a given localdirection relative to the instrument probe 506. The signals from thefield transducer 531 represent the components of a vector 533 pointingfrom the distal end 506 of the instrument probe along the lines ofmagnetic flux impinging on the distal end. Provided that the distal end506 is located in a region reasonably close to one of the poles ofpermanent magnet 530, the vector along the lines of flux pointsgenerally in the direction of site probe body 528. The display (notshown) may display this information as a direction vector. The physicianmust interpret this information as a direction relative to the end ofthe probe. For example, in using a steerable probe of the type discussedabove, the physician can swing the distal end of the probe in variousdirections and find the direction in which the direction vector pointsstraight ahead from the distal end of the instrument probe. Thephysician may then advance the instrument probe and repeat the process.In this way, the instrument probe “homes in” on the site probe.

A site probe according to a further embodiment of the invention includesa probe body 628 with an elongated shaft 629. The field transducer inthis site probe may be an ultrasonic transducer disposed in the in ahandle 631 at the proximal end of shaft 629. Ultrasonic energy suppliedby the field transducer is emitted from the site probe along essentiallythe entire length of the shaft, thus creating a field of ultrasonicenergy surrounding the shaft. The field has progressively diminishingintensity in directions away from the shaft. The instrument probe has afield transducer or position sensor 633 in the form of a microphone orother transducer sensitive to ultrasonic energy. The monitoring systemis arranged to provide a signal, such as an audible signal havingintensity directly related to the intensity of ultrasonic energyimpinging on the field transducer or microphone 633. In this way, thesystem indicates the distance from the tip of the instrument probe tothe shaft 629 of the site probe. The physician can use this informationto guide the instrument probe into proximity with shaft 629 and tomaintain the tip of the instrument probe in proximity with the shaft asthe instrument probe is advanced towards the site probe body 629. In avariant of this approach, the ultrasonic energy is emitted only fromsite probe body 628 itself, so that the ultrasonic field takes the formof a generally spherical field, with the intensity progressivelydiminishing in all directions away from the probe body. In this case,the sensed intensity represents distance from the site probe body 628.This information can be used to guide the instrument probe as, forexample, by moving the instrument probe in various directions anddetecting which direction of movement results in the greatest increasein intensity. Similar approaches can be used with magnetic andelectromagnetic signals radiated from a site probe. The oppositeapproach, in which an acoustic or electromagnetic field is radiated fromthe instrument probe and the intensity of the field impinging on thesite probe is monitored, may also be employed. In either approach, thesignals from the field transducer or sensor on the probe which acts asthe signal receiver indicate the distance between the probes and thusprovide information concerning the disposition of the two probesrelative to one another.

According to further aspects of the invention, information concerningthe relative dispositions of a plurality of probes can be used tocoordinate the action of the plural probes and to guide one or more ofthe probes, regardless of whether any of the probes is fixed to thepatient's body. For example, in the embodiment depicted in FIG. 12 twoinstrumented catheters 690 and 694 are coordinated so that their distalends are juxtaposed with one another. Thus, positional informationderived by position sensors 630 and 632 adjacent the distal tips ofcatheter 690 and 694 is used by the physician to navigate both cathetersinto position adjacent a common treatment location 692. Moreover, theposition sensors 630 and 632 provide information concerning theorientations of both catheters relative to one another and relative tothe common treatment location 692, so that the tips of both catheterscan be aimed onto the common treatment location. Thedisposition-determining systems discussed above with reference to theinstrument probes and site probes can be used to provide informationconcerning the relative dispositions of multiple probes either bymeasuring the disposition of each probe in an external frame ofreference or by monitoring fields transmitted between field transducerson the multiple probes and determining relative dispositions directlyfrom such monitored fields. It is useful to coordinate the actions ofmultiple catheters in catheter-based surgical procedures as, forexample, where multiple different tools must be brought to a commonlocation so that the common location can be treated by all of the tools.Also, one or more of the catheters may carry devices for observing thetreatment as, for example, optical or ultrasonic viewing equipment,whereas the other catheters may carry devices for manipulating, cuttingor excavating tissues. The tissues can be cut or “excavated” by actionof a laser beam directed out of a catheter tip or, alternatively, byapplying small gas bubbles (“microbubbles”) and causing rupture of thesame by applying ultrasonic energy to the area infused withmicrobubbles. Coordinated catheters can be used in such surgicaloperations as, for example, by applying the laser light or microbubblesthrough one catheter and observing the process through another catheter.

As shown in FIG. 13, plural probes can be coordinated with one anotherusing information concerning their relative dispositions even withoutbringing the probes into close proximity to one another. Thus, in theembodiment of FIG. 13, probes 702 and 704 lie on opposite sides of abodily structure, but are aligned and aimed towards one another usingpositional information derived from position sensors or fieldtransducers carried on the probes. Probes pointing towards one anothercan be used for a variety of purposes. For example, probe 702 maytransmit ultrasound to a detector on probe 704 and a detector on probe704 may be actuated to generate an ultrasonic image of the tissuesbetween the probes. Alternatively, probes which are initially disposedat a distance from one another can be aligned with one another and thenone or both of the probes can be advanced towards the other probe, sothat the probes are brought together in much the same manner as the siteprobe and instrument probe discussed above. In this arrangement,however, neither probe is fixed to the body tissue during the procedure.

In procedures according to further embodiments of the invention, two ormore probes can be coordinated by engaging both probes with related bodystructures or with spaced-apart locations in a body structure. Forexample, where a first probe is disposed within an intrabody lumen suchas a vascular structure, the second probe may be disposed in anotherpart of the same lumen. In a procedure according to a further embodimentof the invention using this approach, (FIG. 14), a first probe in theform of a catheter 720 may be threaded through the vascular system andpositioned in an artery within the brain upstream from an aneurysm inthe brain. Catheter 720 may incorporate a first field transducer orposition sensor 722 adjacent its distal end. The step of positioningcatheter 720 may be conducted using conventional imaging techniques suchas fluoroscopic guidance. Alternatively or additionally, the techniquesdisclosed in the '091 Patent may be used. Thus, the disposition of fieldtransducer 722 may be detected by means of fields transmitted to or fromone or more additional field transducers, the detected disposition iscorrelated to the frame of reference of previously-acquired imagingdata, and a representation of the catheter tip is superposed on adisplay showing the image from the previously-acquired data. Aftercatheter 720 is placed, a first medical procedure is performed byinflating a balloon 726 adjacent the distal end of the catheter so as toblock the blood supply to the artery at a first location upstream fromthe aneurysm A. A second probe in the form of a second catheter 726having a field transducer 728 adjacent its distal end is advanced intothe same artery through the surrounding brain tissue from outside of theartery at a second location downstream from the first location. Thesecond probe is then used to place a stent or perform other treatment atthe second location. During placement of the second probe, informationconcerning the relative disposition of the first and second probes canbe used to position the second probe at the desired location withrespect to the first probe, and thereby position the second probe at thedesired location with respect to the artery and aneurysm.

The relative disposition information can be used in conjunction withother sources of disposition information. For example, informationconcerning the disposition of second probe distal end or fieldtransducer 728 relative to first probe distal end or field transducer722 can be used in conjunction with a superposition scheme as describedin the '091 patent, in which a representation of the second probe distalend is displayed in registration with a previously-acquired image. Thesuperposition scheme can be used to guide the second probe aroundstructures such as critical areas of the brain far from the first probe,whereas the relative position information can be used to bring thesecond probe to a precise placement. The relative dispositioninformation can be combined with direct image guidance in similarmanner. Use of relative disposition information in conjunction withother information can be adapted to procedures in other regions of thebody.

Other procedures wherein plural probes are placed on separated butfunctionally related sites include placement of two probes on separatepoints along a nerve for stimulation and measurement of nerve impulsetravel, and placement of an infusion catheter along a blood vessel and asampling catheter in the vascular bed served by that blood vessel. Asdepicted in FIG. 15, more than two probes can be coordinated in asimilar fashion. Thus, in the four-catheter arrangement of FIG. 15,catheter 804 is excavating tissue at a location 806, whereas catheter808 is removing the debris from such location. Catheter 810 is viewingthe tissue surrounding location 806 using an ultrasonic imaging systemcarried on the catheter, whereas catheter 112 is injecting microbubblesinto the vascular bed at location 106 to enhance the contrast betweenvarious types of tissues at such location.

The use of multiple probes is advantageous in that each probe need onlyaccommodate one or a few devices. The individual probes may be simplerand smaller in size than a composite probe incorporating all of therequired devices. The preferred field transducers and probes utilized inaccordance with the present invention desirably are small-diameterdevices to facilitate insertion into the body. Thus, each fieldtransducers desirably has a smallest dimension less than about 3 mm,preferably less than 2 mm, more preferably less than about 1 mm; stillmore preferably less than about 0.2 mm and most preferably even smaller.The probe itself desirably has dimensions, at the field transducer, inthe same ranges. Among the field transducers which can be employed arethose disclosed in copending, commonly assigned United StatesProvisional Patent Application 012,242 Filed Feb. 26, 1996 and in thePCT International Application entitled Catheter With Lumen, namingBiosense, Inc. as an applicant, filed of even date herewith in theUnited States Receiving Office and claiming priority of said '242application, the disclosures of which are hereby incorporated byreference herein.

One medical procedure which can be performed using the techniquesdiscussed above is a liver bypass. Patients who have advanced chirosisof the liver suffer, as a result of blockage of the portal vein, fromelevated venous blood pressure, which may cause fatal GI bleeding. Inthe bypass procedure, a shunt is created between the hepatic vein andthe portal vein in the liver to bypass most of the liver. Thus, thevenous blood pressure is reduced and GI bleeding eliminated. Asdisclosed, for example, by Zemel et al., Technical Advances inTransjugular Intrahepatic Portosystemic Shunts, RadioGraphics, Vol. 12,No. 4, pp. 615-623 (1992), the disclosure of which is incorporated byreference herein, a catheter and guidewire are inserted through thejugular vein into the hepatic vein, and a needle is passed along theguidewire and used to probe for the portal vein. The needle is forciblyadvanced through the liver tissue towards the portal vein. This entailsconsiderable difficulty if the liver tissue is toughened or scarred asoccurs in some diseases. Since the needle is hollow, when the otherportal is found, blood flows through the needle. A catheter may replacethe needle, so that the catheter extends between the veins. A stent suchas an inflatable stent is guided along the needle or catheter to form apermanent passageway connecting the two veins. The opposite procedure,wherein entry is made from the portal vein and the needle is passedthrough the liver tissue to the hepatic vein, can also be employed. Thisprocedure is performed using a fluoroscope and is very lengthy, so theamount of radiation exposure of the patient and the surgeon isconsiderable.

According to further aspects of the present invention, such a procedurecan be greatly facilitated by using non-ionizing radiation transmittedto field transducer on a needle or other probe used to form thepassageway, and determining the disposition of the probe during theprocedure using such non-ionizing radiation. As shown in FIG. 15, aneedle 902 with a field transducer or position sensor 904 thereon isintroduced into the hepatic vein. A site probe 920 having a positionsensor or field transducer 922 thereon is disposed in the liverparenchyma adjacent to the portal vein. The needle is guided toward theportal vein by monitoring the relative dispositions of the needle andmarker catheter in the manner discussed above while the needle isadvanced through the liver tissue. One the needle has penetrated to theportal vein, the remainder of the procedure is performed in theconventional manner. In a further embodiment of the invention, theposition of a needle with a position sensor thereon is monitored and theposition information is registered with a previously-acquired image ofthe patient such as a CT image made using an intravenous contrastmedium. As described in the aforementioned U.S. Pat. No. 5,558,091, suchregistration can be achieved by means of fiducial markers imaged alongwith the patient. As the needle is advanced through the liver tissue, arepresentation of the needle tip is superposed on the displayed image,thereby allowing the physician to guide the needle from the hepatic veintoward the portal vein or vice-versa. In any of the above-describedprocedures for tunneling through the liver tissue, passage of the needlecan be facilitated by destroying the intervening tissue using a laser orby instilling microbubbles into the tissue ahead of the needle andapplying focused ultrasound to destroy the tissue. Where thesetechniques are employed, the needle may be replaced by a flexible devicesuch as a catheter.

As shown in FIG. 17, numerous site probes 1028 a-1028 c with fieldtransducers thereon can be disposed at distant locations within the bodyof the patient to guide one or more instrument probes, also equippedwith field transducers, 1030 to any of these locations. The numerousprobes can also be employed in conjunction with additional fieldtransducers disposed outside of the body, such as reference fieldtransducers 1032 disposed in a fixed frame of reference. In onearrangement, reference field transducers 1032 act as signaltransmitters, whereas the field transducers on all probes 1028 and 1030act as receivers. In other arrangements, the field transducers act astransmitters. Various multiplexing and signal separation arrangementscan be used to avoid interference between the field transducersassociated with the multiple probes. For example, field transducersassociated with each of the site probes 1028 may be low-poweredtransmitting devices such as the re-radiating devices discussed abovewith reference to FIGS. 9 and 9A, and the field transducer of theinstrument probes 1030 may be relatively insensitive receivers, orvice-versa, so that each instrument probe will interact with the closestsite probe but will not interact with other site probes.Frequency-division multiplexing, code diversity multiplexing and timedivision multiplexing, as well as combinations of these multiplexingschemes may be employed. For example, the various reference fieldtransducers 1032 may transmit at different frequencies, whereas each ofthe field transducers 1028 a, 1028 b and 1028 c of the site probes maytransmit at other frequencies, these frequencies being different fromone another. Alternatively or additionally, the various fieldtransducers used in a single procedure may use different types offields. Thus, the field transducers associated with some of the probesmay be transmit or receive optical or acoustic fields, whereas othersmay transmit or receive magnetic or electromagnetic fields. In theembodiment of FIG. 17, and in the other embodiments discussed above, thesame field transducer of the instrument probe 1030 may be used both toestablish disposition relative to site probes 1028 and to establishposition in the frame of reference of reference transducers 1032 as, forexample, for use in displaying position of the instrument probesuperposed on an image of the patient.

As also illustrated in FIG. 17, cardiac pacemaker lead 1040 is providedwith a field transducer 1042 adjacent the distal tip of the lead. Thecardiac pacemaker lead is implanted for long-term use in theconventional manner. Desirably, transducer 1042 is arranged so that itcan operate without a lead-supplied power source. For example,transducer 1042 may be a permanent magnet or reradiating fieldtransducer as discussed above. Thus, even if lead 1040 breaks, aninstrument probe may be brought into proximity with the distal end andused to remove the distal end. The same techniques can be used to markother implanted devices such as orthopedic implants, and tools which arenot deliberately implanted but which may be accidentally lost duringsurgery.

A preferred screen display for indicating the relative dispositions ofprobes is depicted in FIG. 18. This may be used in place of the arrow306 discussed above with reference to FIG. 5. A display device such as acomputer screen 1100 shows a representation 1102 of a site probedisposed within the patient and a representation 1104 of an instrumentprobe being guided toward the patient. Optionally, both of theserepresentations are displayed against a background of grid lines 1106representing Cartesian (x-y-z) coordinates of a reference coordinatesystem such as the coordinate system of the external field transducers.Thus, the site probe representation 1102 may be in the form of a sphereor other arbitrary shape. Instrument probe representation 1104 includesa sighting aperture 1108 in the form of a circle or other closed orsemi-closed geometric figure, as well as crossing lines 1110 and 1112representing directions perpendicular to the a preselected axis of theinstrument probe, preferably the long axis of the probe at the tip ofthe probe. The directions of lines 1110 and 1112 may correspond to thepitch and yaw axes 239 and 241 (FIG. 4) of the instrument probe. Thesedirections are fixed with respect to the instrument probe distal tip, sothat when the instrument probe rolls around its long axis, thedirections of lines 1110 and 1112 move in the same manner. One end 1112a of line 1112 has a different appearance from the other lines so thatthe user can track the roll orientation of the instrument probe tipvisually. Pitch and yaw movements of the instrument probe distal tip,around axes 239 and 241, (FIG. 4) are shown by movement of thecoordinate system and site probe representation relative to the screenand relative to the instrument probe representation 1104. Thus, the viewof grid lines 1106 representing the coordinate system, as well as theview of site probe representation 1102 which is displayed on the screenis a projection in a plane perpendicular to the long axis of theinstrument probe at the tip of the probe. By moving and/or bending theinstrument probe so that the site probe representation is aligned withthe instrument probe representation, as by centering sphere 1102 incircle 1108 of instrument probe representation 1104, the physician canpoint the instrument probe long axis or roll axis 237 (FIG. 4) directlyat the site probe. Advancement of the instrument probe in this conditionwill bring the instrument probe directly towards the site probe. Thephysician can use the displayed information to navigate the instrumentprobe to one side of the site probe.

Distance between the tip of the instrument probe and the site probe isrepresented by the size of the site probe representation 1102 relativeto the instrument probe representation 1104. Preferably, the instrumentprobe representation has a fixed size, whereas the site proberepresentation grows as the distance decreases and shrinks as thedistance decreases. In a particularly preferred arrangement, the siteprobe representation completely fills circle 1108 when the tip is at thesite probe. Other representations of distance, such as alphanumericdisplay 1114 and bar graph 1116 are also provided. As these and othervariations and combinations of the features described above can beutilized without departing from the present invention, the foregoingdescription of the preferred embodiments should be taken by way ofillustration rather than by way of limitation of the invention asdefined by the claims.

INDUSTRIAL APPLICABILITY

The invention can be used in medical and related procedures.

What is claimed is:
 1. A method of guiding a probe in the body of apatient comprising the steps of: (a) providing a site probe at a sitewithin the body of a patient and providing a instrument probe to beguided within the body of the patient; (b) transmitting one or morenon-ionizing fields to or from each of said probes and detecting eachsuch transmitted field; and (c) determining the relative disposition ofsaid instrument probe and said site probe by determining a position ofeach said probe in a common frame of reference based upon the propertiesof said detected fields and determining said relative disposition basedupon the so-determined positions; and (d) directing said instrumentprobe toward said site probe based on relative deposition.
 2. A methodas claimed in claim 1 wherein said directing step includes the step ofpointing said instrument probe toward said site probe.
 3. A method asclaimed in 1 wherein said directing step includes the step of movingsaid instrument probe toward said site probe.
 4. A method as claimed inclaim 3 wherein said transmitting step includes the step of generatingmagnetic fields at said external elements and said detecting stepincludes the step of detecting said magnetic fields at said probes.
 5. Amethod as claimed in claim 3 wherein said determining step includes thesteps of calculating the position of each said probe in said frame ofreference and calculating a distance and direction between saidinstrument and said site from said positions.
 6. A method as claimed inclaim 1 further comprising the step of providing one or more elementsexternal to the body of the patient defining said frame of reference,said step of transmitting said fields to or from said probes includingthe step of transmitting said fields between said probes and saidexternal elements so that at least one property of each such detectedfield depends upon the dispositions of said probes relative to said oneor more external elements.
 7. A method as claimed in claim 1 furthercomprising the steps of placing a reference probe in or on the body ofthe patient, said transmitting and detecting steps including the stepsof transmitting one or more fields to or from said reference probe, anddetecting such fields so that at least one property of the detectedfields depends upon a disposition of said reference probe, the methodfurther comprising the step of determining a relative disposition ofsaid reference probe and said site probe based upon one or moreproperties of detected fields.
 8. A method as claimed in claim 7 whereinsaid steps of placing said site probe and said reference probe includethe step of placing said reference probe adjacent said site probe.
 9. Amethod as claimed in claim 8 wherein both said site probe and saidreference probe are placed on or adjacent to a lesion.
 10. A method asclaimed in claim 7 further comprising the step of providing a warningsignal in response to a change in said spatial relationship between saidsite probe and said reference probe.
 11. A method as claimed in claim 7further comprising the step of determining a relative disposition ofsaid site probe and said reference probe by imaging the patient andproviding a warning signal if the spatial relationship determined basedupon said detected fields is different than the spatial relationshipdetermined in said imaging step.
 12. A method of guiding a probe in amedical patient comprising the steps of: (a) providing a site probe at asite within the body of a patient and providing a instrument probe to beguided within the body of the patient; (b) transmitting one or moremagnetic fields to or from each of said probes and detecting each suchtransmitted field; (c) determining the relative disposition of said siteprobe and said instrument probe from the properties of said detectedfields; (d) providing an indication of said relative disposition; and(e) moving said instrument probe within the body of the patient towardsaid site in response to said indication.
 13. A method as claimed inclaim 12 wherein said step of providing an indication includes the stepof providing said indication in human-perceptible form and said movingstep includes the step of manually controlling movement of theinstrument probe within the body in response to said indication.
 14. Amethod as claimed in claim 12 wherein said step of providing saidindication includes the step of providing said indication in the form ofone or more audible signals.
 15. A method as claimed in claim 12 whereinsaid moving step includes the step of automatically controlling movementof the instrument within the body in response to said indication.
 16. Amethod as claimed in claim 12 wherein said step of providing said probesincludes the step of imaging the patient's body and placing said siteprobe at said site using the data in said image.
 17. A method as claimedin claim 16 wherein said placing step is conducted during the imagingstep and said imaging step is performed so that said site probe isincluded in said image.
 18. A method as claimed in claim 17 wherein saidsite is a site adjacent a lesion, said imaging step being performed sothat said lesion is included in the image, the method further includingthe step of treating the lesion using said instrument probe after saidmoving step, whereby the instrument is guided to the lesion during saidmoving step.
 19. A method as claimed in claim 13 wherein said step ofdetermining relative disposition includes the step of determiningdistance between said instrument and said site.
 20. A method as claimedin claim 19 wherein said step of determining relative dispositionincludes the step of determining only said distance, without determiningdirection from said instrument to said site.
 21. A method as claimed inclaim 20 wherein said step of determining relative disposition includesthe step of determining direction from said instrument to said site. 22.A method as claimed in claim 12 wherein said transmitting, detecting anddetermining steps and said step of providing said perceptible indicationare performed during said moving step so as to alter said perceptibleindication in real time as the instrument moves.
 23. A method ofcoordinating two probes, comprising: (a) providing a first and secondprobe, each of which has a field transducer mounted thereon; (b)performing a first medical procedure at a first location using the firstprobe; (c) performing a second medical procedure at a second locationusing the second probe; (d) determining the relative positions of theprobes in a common frame of reference by transmitting one or morenon-ionizing magnetic fields to or from said field transducers on saidprobes; and (e) coordinating the two medical procedures using thedetermined relative positions in the common frame of reference.
 24. Amethod according to claim 23, wherein the second probe is a microbubbleinjecting probe.
 25. A method according to claim 23, wherein said stepof determining the relative positions of the probes comprises: (a)determining the position of the first probe using non-ionizing magneticradiation; (b) determining the position of the second probe usingnon-ionizing magnetic radiation; and (c) subtracting the two positions.26. A method of displaying the relative positions of an instrument and asite within the body of a living subject for directing the instrumenttoward the site comprising the steps of: (a) providing an arbitraryrepresentation of the instrument on a planar display; (b) providing aprojection of space in a plane perpendicular to an axis of theinstrument on said display, said projection of space including anarbitrary representation of the site, said projection being selected sothat said representation of said site is aligned with saidrepresentation of the instrument when said axis of said instrument isaligned with said site; and (c) altering the relative sizes of said siterepresentation relative to said instrument representation as distancebetween said instrument and said site change.
 27. A method as claimed inclaim 26 wherein said altering step is conducted so that the size of thesite representation increases as said distance decreases.
 28. A methodas claimed in claim 26 wherein said projection of space includesrepresentations of a fixed coordinate system, whereby said fixedcoordinate representations will move on said display as orientation ofsaid axis of said instrument changes.
 29. A method of coordinating aplurality of probes, comprising: (a) providing a first probe, a secondprobe, and a third probe each of which has a field transducer mountedthereon; (b) performing a first medical procedure at a first locationusing the first probe; (c) performing a second medical procedure at asecond location using the second probe; (d) performing a third medicalprocedure at a third location using the third probe, wherein the thirdmedical procedure is coordinated with the two medical procedures; (e)determining the relative positions of the probes by transmitting one ormore nonionizing fields to or from said field transducers on saidprobes; and (f) coordinating the medical procedures using the determinedrelative positions.
 30. A method of coordinating two probes, comprising;(a) providing a first and second probe, each of which has a fieldtransducer mounted thereon, wherein the second probe is an ultrasonicimaging probe; (b) performing a first medical procedure at a firstlocation using the first probe; (c) performing a second medicalprocedure at a second location using the second probe; (d) determiningthe relative positions of the probes by transmitting one or morenon-ionizing fields to or from said field transducers on said probes;and (e) coordinating the two medical procedures using the determinedrelative positions.
 31. A method of coordinating two probes, comprising:(a) providing a first and second probe, each of which has a fieldtransducer mounted thereon; (b) performing a first medical procedure ata first location using the first probe; (c) performing a second medicalprocedure at a second location using the second probe; (d) determiningthe relative positions of the probes by transmitting one or morenon-ionizing fields to or from said field transducers on said probes;and (e) coordinating the two medical procedures using the determinedrelative positions wherein the medical procedure performed using saidfirst probe forms debris and said second probe is a vacuuming probewhich removes said debris.